(一) can/could1. 表示能夠做某事(具備某種能力)(could主要指過(guò)去);2. 表許可; 用于疑問(wèn)句表示請(qǐng)求(could表示語(yǔ)氣更加婉轉(zhuǎn));用于否定句表示不允許。3. can還可表一時(shí)的可能性。【考例1】I’m going to Europe on vacation together with John if I ______ find the money. (2012全國(guó)II)A. can B. might C. would D. need解析：Acan在句中意為“能夠”。【考例2】Peter ______ be really difficult at times even though he’s a nice person in general. (2008遼寧)A. shall B. should C. can D. must解析：Ccan在句中表“可能”。(二) must1. must用于肯定句中表示說(shuō)話人的意志或義務(wù)，或者堅(jiān)決要求某人做某事，意為 “必須”;mustn’t表示“禁止”。2. 在以must開(kāi)頭的疑問(wèn)句中，肯定回答用must;否定回答用needn’t 或don’t have to，表示“不必”。3. 另外還有一種含義為“偏要”。表示說(shuō)話人生氣或不滿的情緒?！究祭?】—Shall I inform him of the change of the schedule right now?—I am afraid you ______, in case he comes late for the meeting. (2011福建)A. will B. must C. may D. can解析： B。must意為“必須”?！究祭?】—______ you interrupt now? Can’t you see I’m on the phone?—Sorry Sir, but it’s urgent. (2012重慶)A. Can B. Should C. Must D. Would解析：C。must在句中意為“偏要，非要”。(三) will / wouldwill (would) 表意愿, 用于各種人稱(chēng)的陳述句，還可表示某種習(xí)慣，或在疑問(wèn)句中提出請(qǐng)求。主語(yǔ)為物時(shí)，可意為“不起作用”?！究祭緿ays later, my brother called to say he was all right, but ______ say where he was. (2012江蘇)A. mustn’t B. shouldn’t C. wouldn’t D. mightn’t解析：C。would在句中為will的過(guò)去式，表意愿。(四) may / might表示允許，和can/could一樣，可用于各種人稱(chēng)。但要注意：在疑問(wèn)句中will/would表示征詢(xún)對(duì)方許可或提出請(qǐng)求時(shí)，常用于第二人稱(chēng), would / might/could形式常表語(yǔ)氣委婉，不表示過(guò)去時(shí)態(tài)。【考例】—______ I take the book out?—I’m afraid not. (2010四川)A. Will B. May C. Must D. Need解析：B。will/would 用于第二人稱(chēng)表示“請(qǐng)求”;而may可用于各種人稱(chēng)。(五) shall/should1. shall用于二、三人稱(chēng)，表示“命令、威脅、警告、強(qiáng)制、允諾”等。2. 在疑問(wèn)句中， shall用來(lái)征詢(xún)意見(jiàn)或請(qǐng)求指示，用于第一和第三人稱(chēng)。3. shall常用在主語(yǔ)是第三人稱(chēng)的條約、法律法規(guī)、規(guī)章制度等文件中表示“義務(wù)”或“規(guī)定”。4. should 用于勸告、建議的目的時(shí)，可譯成“應(yīng)該”，表示主觀情況。【考例】One of our rules is that every student ______ wear school uniform while at school. (2012遼寧)A. might B. could C. shall D. will解析：C。shall在句中表示“義務(wù)”或 “規(guī)定”，意為“應(yīng)該，必須”?？键c(diǎn)二、表推測(cè)的情態(tài)動(dòng)詞(一) 對(duì)現(xiàn)在的情況或客觀事實(shí)推測(cè)1. 對(duì)現(xiàn)在或客觀事實(shí)的肯定推測(cè)must意為“肯定、準(zhǔn)是、想必是”;should意為“很可能、該……”，指按常理推測(cè);may(might)意為“也許、大概”，表示把握不大的推斷;can/could可用于疑問(wèn)句表示懷疑(could則表示更不確定);could還表示現(xiàn)在或?qū)?lái)的可能性。【考例1】—What are you doing this Saturday?—I’m not sure, but I _____ go to the Rolling Stones concert. (2013重慶)A. must B. would C. should D. might解析：D。might意為“可能”。【考例2】—Good morning. I’ve got an appointment with Miss Smith in the Personnel Department.—Ah, good morning. You _____ be Mrs. Peters. (2010北京)A. might B. must C. would D. can解析：B。答語(yǔ)句意：哦，早上好。你一定是Peters夫人了。2. 對(duì)現(xiàn)在情況或客觀事實(shí)的否定推測(cè)can’t意為“不可能”、“想必不會(huì)”，表示推測(cè)的語(yǔ)氣相當(dāng)有把握;couldn’t也可有此用法，但語(yǔ)氣委婉。 may not, might not意為“可能不”、 “也許不”，表示推測(cè)的語(yǔ)氣不很有把握?！究祭縄t ______ be the postman at the door. It’s only six o’clock. (2011江西)A. mustn’t B. can’t C. won’t D. needn’t解析：B。句意：門(mén)口的不可能是郵遞員，現(xiàn)在只有六點(diǎn)鐘。(二)對(duì)過(guò)去情況的推測(cè)1. must have done過(guò)去一定做過(guò)某事;2. can’t have done/couldn’t have done過(guò)去不可能做過(guò)，肯定沒(méi)做過(guò)某事;3. can/could have done用于疑問(wèn)句中表示對(duì)過(guò)去發(fā)生的事情或狀態(tài)的推測(cè);4. could have done 過(guò)去可能做過(guò)某事;5. may / might (not) + have done過(guò)去可能(沒(méi))做過(guò)某事?！究祭縎ince nobody gave him any help, he _____ have done the research on his own. (2013課標(biāo)2)A. can B. must C. would D. need解析：B。句意：因?yàn)闆](méi)有人給予任何幫助，他一定是獨(dú)立完成這項(xiàng)研究的?？键c(diǎn)三、“情態(tài)動(dòng)詞+have+過(guò)去分詞”的其他用法1. should /ought to have done表示過(guò)去本應(yīng)該做某事卻沒(méi)有做。2. shouldn’t /ought not to have done 表示本不應(yīng)該做某事卻做了。3. could have done在肯定句中還可表示“本來(lái)可以/可能做成某事”。4. might have done可表示本來(lái)可能，但實(shí)際上沒(méi)有發(fā)生的事。5. needn’t have done表示“本來(lái)不需要做某事而做了”。【考例】We ______ the difficulty together, but why didn’t you tell me? (2012北京)A. should face B. might face C. could have faced D. must have faced解析：C。句意：我們本可以一起面對(duì)困境的，可是你為什么不告訴我呢?